Communication apparatuses that operate in communication with other devices have been widespread. For example, some techniques have been proposed that enable indoor units and an outdoor unit, which are air conditioners constituting an air conditioning system, to communicate with each other and thus operate in cooperation with each other (for example, refer to Patent Literature 1).
Patent Literature 1 discloses a system involving the indoor units and the outdoor unit that are connected to each other with a three-core cable including a power source line, a communication line, and a shared line. In this system, the air conditioners are supplied with electric power through the power source line and the shared line and communicate with each other through the communication line and the shared line.